JPS58204136A - Tuyere for blowing gas - Google Patents

Abstract

PURPOSE:To blow gas economically and efficiently into molten metal from a tuyere attached to the bottom or side wall of a vessel without clogging the tuyere by using a carbonaceous refractory as the material of the tuyere. CONSTITUTION:A tuyere 1 made of a carbonaceous refractory for blowing gas is manufactured by binding many carbon fibers in a carbon cylinder or the like. The gaps among the fibers are used as holes 2 for passing gas. Pitch or tar may be mixed with fine wires of a low m.p. metal, extruded, and calcined to manufacture a porous tuyere. Piping 4 for blowing gas is connected to the bottom of the tuyere 1 having many fine holes 2 with a metallic sealing part 3 in-between, and the tuyere 1 is attached to a ladle. Thus, the tuyere 1 is provided with superior spalling resistance, etc. as well as sufficient gas permeability.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gas blowing tuyere for blowing gas into molten metal contained in a container.

In the production of steel, gas injection into molten metal has become an indispensable technology for the production of high-grade steel and its stable operation, including uniformity of quality, promotion of reactions, and removal of inclusions by floating. There is.

Such gas injection into the molten metal has conventionally been carried out using a method such as a bottom method.

(1) A method of blowing gas into molten metal using a lance inserted from above.

(2) A method in which large-diameter through holes are provided in the bottom wall or side wall of the container, and gas is blown through the through holes.

(3) A method of attaching a porous plug to the bottom wall or side wall of the container and blowing gas through this porous plug.

(4) A method in which a large micropore refractory is attached to the bottom or side wall of the container and gas is blown through the micropore refractory.

However, in the method (1) above, gas is blown into the molten metal using a lance whose tip is immersed, so the lance is never worn out due to melting damage caused by slag or metal or cracking due to thermal stress. , there is a problem in that durability is low.

Method (2) above requires continuous gas injection while the molten metal is contained in the container, which is inconvenient because gas injection cannot be interrupted, and gas is continuously blown. However, there is also the problem that molten metal intrudes into the through pores and closes the through pores.

Since method (3) above uses the slits formed between the particles of the refractory material as ventilation holes, it generally does not provide sufficient ventilation, and in order to reduce the ventilation, it is necessary to If the diameter of the pores is increased, there is a problem in that molten metal enters and solidifies into the vent hole, clogging the vent hole, and also causes erosion and cracking, resulting in low durability.

The method (4) above involves embedding fine through-hole-forming materials such as paper or fibers in, for example, alumina-8iC-based highly flammable materials and firing them. A refractory material having through holes of uniform diameter is made, and gas is blown through the through holes.

According to this method, the durability of refractories is slightly revised, but when the container is used both for transporting molten metal and for refining, the process of receiving molten metal in the container and discharging it after refining is repeated. There is a problem in that thermal stress is generated at the mouth, which reduces spall resistance. Further, when an alumina-SiC refractory is used in a container containing hot metal, SiC in the refractory becomes a source of Si addition to the hot metal. Therefore,
During hot metal pretreatment such as deP and S removal, it is essential that most of the Si in the hot metal be removed.
Such migration of Si into the hot metal is undesirable.

This invention allows sufficient gas to be blown into the molten metal contained in the container for the refining process from point d as described above, thereby preventing the molten metal from penetrating into the vent hole and clogging it. In addition to being able to interrupt gas injection at any time, the gas injection lining is made of a highly durable refractory material that is resistant to thermal shock and has excellent corrosion resistance. It must be made of refractory material (having special characteristics).

Carbonaceous refractories include A403-5in2 refractories used in conventional gas injection tuyeres and At20. -Si
Compared to C-based refractories, it has poor wettability with molten metal.

Therefore, the gas blowing tuyeres made of carbonaceous refractories can increase the maximum diameter of the vent hole through which molten metal does not penetrate when there is no gas blowing area, compared to the conventional gas blowing tuyeres.

Generally, the maximum pore diameter that does not allow molten metal to penetrate is derived from the following equation.

However, P: Molten metal head pressure (dyn/c++ r: Radius of pores in the refractory T: Surface tension of the molten metal (dyn/cm ) θ: Contact angle between the molten metal and the refractory For example, when molten metal is placed in a container The temperature of hot metal is 1500℃.
℃, surface tension 18. OOclyn/cm, specific gravity 6
．． 5. When the head is 3 m and the carbonaceous refractory of the present invention is used, the maximum pore diameter at which molten metal does not penetrate is calculated using the above formula (1) along with the conventional example.
It will be as shown in Table 1 below.

Note: Hot metal penetrated even if the pore diameter was small.

As can be seen from the first paragraph above, when the carbonaceous refractory of the present invention is used, the refractory is difficult to wet with molten metal, and therefore the maximum pore diameter that prevents molten metal from penetrating must be significantly increased. was completed.

Furthermore, carbonaceous refractories have higher thermal conductivity than conventional alumina refractories. Table 2 compares the thermal properties of car&n (graphite) and alumina (At20M).

As can be seen from the second column of Table 2, the thermal conductivity of carbon (graphite) is more than 20 times that of alumina (At203), and the coefficient of thermal expansion is about half that of alumina. Therefore, the gas-injected lining made of the carbonaceous refractory of the present invention is highly resistant to thermal shock and does not cause any cracks or the like.

Such gas injection panels made of carbonaceous refractories are manufactured by, for example, binding a large number of carbon fibers into a carbon cylinder or the like, and using the gaps between the fibers as gas ventilation holes.
I) It can be manufactured by mixing thin wires of low melting point metal with pitch or tar and extruding and firing the mixture to make it porous.

FIG. 1 is a perspective view of the gas injection tuyere of the present invention, in which a large number of fine ventilation holes 2 are formed in the gas injection tuyere 1 made of carbonaceous refractory material, and the bottom of the tuyere 1 is made of a carbonaceous refractory. A gas injection pipe 4 is connected via a metal seal 3. FIG. 2 shows a ladle to which this gas blowing tuyere 1 is attached. Two tuyeres 1 are provided at the bottom 5a of the ladle 5, and a gas guiding pipe 4 is connected to each of them.

Next, this invention will be explained in detail. De-P, de-S for hot metal
Approximately 1300°C held in a container for processing
Soda ash was added to hot metal at a temperature of , and inert gas was blown into the hot metal. Table 3 shows the amount of erosion and spalling resistance (
cracks) and durability, and the condition of the joints after heating and cooling.

In Table 3, ◯ indicates good, Δ indicates slightly poor, and × indicates poor. As can be seen from Table 3, when the gas injection tuyeres made of the carbonaceous refractory of the present invention are used, the amount of erosion is extremely small, the spalling resistance is excellent, and the durability is high. Indicated.

Next, the effects of this invention will be described.

(1) Conventional porous plugs made of refractory materials have poor wettability with molten metal, making it difficult for molten metal to penetrate into the vent holes even when gas is not blown. It can also be made into a dog, providing sufficient ventilation.

(2) Due to its high thermal conductivity, it is resistant to thermal shock and has excellent spall resistance.

(3) Compared to conventional refractory materials, it has lower reactivity with molten metal, so it has extremely excellent erosion resistance, especially when the molten metal is hot metal.

(4) Since it has better workability than conventional refractory materials, it is easy to manufacture and provides a lining with excellent dimensional accuracy.

(5) Since molten metal does not penetrate into the vent hole even when gas is not blown, there is no need to blow a small amount of gas during transportation of the container as in the past, and the vent hole can be closed. Therefore, gas blowing can be carried out in a short time, and the work of blowing gas into molten metal can be carried out economically and efficiently.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a gas blowing tuyere of the present invention, and FIG. 2 is a perspective view of a ladle to which the gas blowing tuyere is attached. In the drawings, 1...Tuyere for gas blowing 2...Through hole 3...
Seal part 4...Piping 5...Ladle
5a... Ladle bottom applicant: Nippon Kokan Co., Ltd. agent Keita Tsutsumi and one other person

Claims (1)

[Claims] A gas blowing tuyere made of a refractory material and having a vent hole for blowing gas into the container, which is provided on the bottom wall or side wall of a container containing molten metal, the material of which is carbonaceous. A tuyere for gas injection characterized by being made of a refractory material.